Know About SQL Server Database Compatibility Level Performance

Andrew Jackson | Modified: November 19th, 2018 | SQL |

Overview:

SQL server compatibility Level is an advance feature to maintain the performance of the server. Each version of SQL server has this feature but, depending upon the server version, there are variations in values of this feature. By executing the following command, user can itself set the compatibility value in their own server:

compatibility value

where, database_name means mentioning the name of your database
Compatibility_Level = { 130 | 120 | 110 | 100 | 90 } means defining the SQL Server version with which your database is to be made compatible
Moreover, with help of the following command users can determine the Database Engine version with which they are presently connected:

Server_Property

SQL Server Database Compatibility Level Affects

Many users think that impact of compatibility feature is on the entire server, but it is not true. Instead of impacting the entire server, the feature affects the behavior of selected database (that is currently in use). In earlier SQL Server versions, the level acts as a part in backward end. But with change in time and rise in new technologies, it is now not only a part but is now upgraded to a mode i.e. compatibility mode. Some new features that affects the query in the server are added to this mode. This upgradation in the server is discovered in order to minimize the risks, which results in degradation of the server performance.

NOTE: Compatibility mode is a mechanism with which applications or database becomes compatible with upgraded versions of the program. It adjusts the settings of machine/application in such a way that database of any SQL server version can be accessed on any version.

On the basis of application, the aim is to use compatibility level as a means to migrate database from one SQL server version to another without any issue. In other words, the database is made compatible in such a way that it is suited by newer version of SQL server. If the current server applications gets affected by behavioral difference of SQL server versions, then users can convert that application into new compatibility mode. For performing such conversion, users will have to execute set command of Compatibility level that is being discussed earlier.

Tips While Using Compatibility Feature

    • While you are performing modifications on compatibility level and at the same time a query is compiling; in such case you will face an incorrect result & hence, harm to the current database.
    • To get rid of such incorrect results and perform changes in database compatibility level, go through the following steps:
      1. Change the mode of database to single-user access with help of following command:
        Single-User Access
      2. Now alter the database compatibility level
      3. Again, modify the mode of database to multi-user access with help of following statement:
        multi-user
    • To determine SQL Server compatibility level value of present database execute the following statement:

compatibility level value

Operations Performed on SQL Server Compatibility Level

To handle the SQL server database compatibility level performance, the server allow its user to perform different operations on Compatibility level. Following are the operations that can be performed on this level:

NOTE: Assume that we are using SQL server 2012 version

    1. Alteration in Compatibility Level: One can change the level of any database from server by using following statement:
      Alteration in Compatibility Level
    2. Setting Language Under Value 120: Using following statement you can set language and date in the server. But this command is limited to compatibility level 120.
      Setting Language Under Value 120:
      When Compatibility Level is Less than 120
      When Compatibility Level is set to 120

When Compatibility Level is set to 120

    1. Creation of an Infinite Loop: For compatibility level 110 and lower values, on RHS of Except clause user can create an infinite loop with help of following command:
      Creation of an Infinite Loop
    2. Applying Different Font Styles: This shows complete variations in styles with help of following statements:

Creation of an Infinite Loop

Observational Verdict

To handle the performance of server, applications related to server, queries, etc., user is provided with SQL Server Compatibility level feature. The feature allow users to change the value of this level with many other operations. In this blog, all about this feature with its functioning is described.